First you must Decide what your company needs in regards to online marketing and SEO services before you proceed to hire an SEO company to do the work. Do you need link removal, reputation management, a one time SEO audit, ongoing SEO, link building, content marketing. Start by figuring out the job to be done by the SEO company that you are going to hire. Do you want to grow sales or leads, is your goal increased rankings. Have a goal in mind by which you will measure the success of your engagement with your SEO firm, and make that goal the center of your communication with them.